Lowrance tell me to mount the sounder wit hthe centreline level with the bottom of the boat. Belagio would be calling me for advice on their next display if I left it there.

I raise it 1/2" so the botom of the sounder is now level with the boat, and I still have an A- frame + antenna high fountain.

As this could go on a while, could anyone whose transom is accessible give me a couple of measurements -
1) height of bottom of sounder unit wrt bottom of boat
2) distance form transom to leading edge of sounder.

I just want to get a feel for how much further up I need to move it. Unless they all produce jetski style tails?

Always had this problem myself despite experimenting with different heights and angles. In the end I just went with the position that gave the sounder best performance. I've just had a shroud made up to fit on the transom above the transducer to stop the side of my engine cowel getting sprayed all the time.

Lowrance tell me to mount the sounder wit hthe centreline level with the bottom of the boat. Belagio would be calling me for advice on their next display if I left it there.

I raise it 1/2" so the botom of the sounder is now level with the boat, and I still have an A- frame + antenna high fountain.

As this could go on a while, could anyone whose transom is accessible give me a couple of measurements -
1) height of bottom of sounder unit wrt bottom of boat
2) distance form transom to leading edge of sounder.

I just want to get a feel for how much further up I need to move it. Unless they all produce jetski style tails?

A bit off piste, but have you considered bonding the transducer to the inside of the hull? IMHO & experience, you get far better results at higher speeds if it's done correctly & you can find a good mounting spot.

__________________
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4: See rule#5

A bit off piste, but have you considered bonding the transducer to the inside of the hull? IMHO & experience, you get far better results at higher speeds if it's done correctly & you can find a good mounting spot.

Airmar P79 is less than $100 or building your own reservoir and bonding the skimmer transducer is pretty easy too.

I'm running a skimmer ducer on my al hull. The hull at the back of the motor pod (the bottom of the pod is an extension of the hull material, so at the same level) has a 1.5" lip. The ducer is mounted to a block of plastic that is screwed and glued with the screws coming up through the lip (to avoid holes to the inside of the boat.)

The ducer sits about even with the bottom of the hull; a line extended from the bottom of the hull running surface hits the ducer pod just about at the widest part of the oval cross section. As far as setback, I'm using the factory bracket, and it is mounted even with the rear of the bottom lip (I suspect this doesn't have a whole lot to do with your problem.) I found that running the trailing edge of the ducer a click down from flat works best for me.

The white stuff in the pic is a slathering of epoxy covering some SS wire reinforcement, made necessary after hitting a piece of lumber on a return from a fireworks show in SF Bay one night. Snapped the ducer at the marrow part of the arm.

A bit off piste, but have you considered bonding the transducer to the inside of the hull?

Would do, but as my hull is of 1980s vinatage, (no drain well) the only place I can get a "clear shot" through the fibreglass etc (i.e clear of the void) is so far off centreline that it isn't in the water when on the plane!

Jyaski,
I had thought of 'glassing a surface off the transom so it was better protected, but thought I would try a "standard" fit first. I had noticed two "dropouts" at speed on the test run, so may need todrop it back in a bit

Would do, but as my hull is of 1980s vinatage, (no drain well) the only place I can get a "clear shot" through the fibreglass etc (i.e clear of the void) is so far off centreline that it isn't in the water when on the plane!

My transducer is under the deck bonded directly to the hull. I had a Bailey Hatch put in the deck to give me access. I know I'm banging on about it, but it really was a revelation to me having a "thru hull" It solves so many problems.

__________________
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4: See rule#5